Diffusers are known in the art. Diffusers are for widely scattering and/or spreading light, and are used in many different optical application including but not limited to wrist watches, projection systems, displays (e.g., LCDs), computer screens, surgical equipment, optical communication systems, light sensors, fiber optic systems, microscope illumination systems, light guides, and so forth.
Many optical devices such as projection systems, computer screens, surgical equipment, LCDs, communication systems, microscope illumination systems and/or the like use bright light source(s) for illumination or the like. Diffusion of light is often desired in such illumination systems. The light exiting the diffuser in such a system is desired to be highly diffused as it passes through the media or toward the desired structure, as otherwise the illumination of the structure will not be sufficiently uniform. Plastic diffusers have been used in certain applications. However, the use of plastic diffuser sheets is difficult due to the high temperatures which may be experienced within the illumination unit.
Thus, it will be appreciated that there exists a need in the art for diffusers that are not based on plastic.
In certain example embodiments, a diffuser is provided that includes a glass substrate with a diffusing coating thereon. The diffusing coating may include one or more layers. In certain example embodiments, the diffusing coating comprises inorganic pigments therein for light diffusing purposes, and the inorganic pigments are sized so as to permit a diffuser having a combination of high visible transmission and good diffusion qualities to be realized. In certain example embodiments, the diffusing coating may be of or include a frit (e.g., glass frit) with the inorganic pigments therein.
The diffusing properties of the diffuser depend on the scattering of light by particles in the coating. Hence, there is a need of an understanding of the effect of particle size of the inorganic pigments in the coating on diffusing performance, while still permitting an adequate amount of transparency in the visible region of the diffuser to be realized. For example and without limitation, the inorganic pigments of the diffusing coating may be of or include one or more of alumina, zinc oxide, cerium dioxide, titanium dioxide, silicon dioxide, and the like, and can be used as scattering centers for the diffuser.
In certain example embodiments, the diffuser may also include an optional UV (ultraviolet) coating(s) that blocks significant amounts of UV radiation thereby reducing the amount of UV radiation which can makes its way through the diffuser. The UV coating may be provided separate from or as part of the light diffusing coating.
Diffusers according to certain example embodiments may be used in an illumination system in any suitable optical application, including but not limited to applications such as wrist watches, projection systems, display backlights, computer screens, surgical equipment, optical communication systems, light sensors, fiber optic systems, microscope illumination systems, and light guides.
In certain example embodiments, there is provided an illumination system comprising: a light source for emitting light, the light emitted from the light source including at least visible light and ultraviolet (UV) radiation; a diffuser positioned so as to receive light from the light source, the diffuser diffusing visible light received from the light source; wherein the diffuser comprises a glass substrate that supports a light diffusing coating, the light diffusing coating comprising inorganic pigment particles mixed with a frit matrix; and wherein the diffuser has a diffusing property F(Q) of greater than 0.100 (more preferably greater than 0.102, even more preferably greater than 0.110, and sometimes greater than 0.125, 0.200 or 0.250) and a visible transmission of at least 57% (more preferably at least 58%, 60%, or 61%), where F(Q) is defined by: F(Q)=1/[4({θmax−θmin}/W)2+1] where W is a half width at a half maximum value point of a illumination vs. diffusing angle plot, θmax is a maximum value of the illumination vs. diffusing angle plot, and θmin is a minimum of at least one of the tails of the illumination vs. diffusing angle plot.
In other example embodiments, there is provided an illumination system comprising: a light source for emitting light; a diffuser positioned so as to receive light from the light source, the diffuser diffusing visible light received from the light source; and wherein the diffuser comprises a glass substrate that supports a light diffusing coating, the light diffusing coating comprising inorganic pigment particles mixed with frit.